1. Field of the Invention
The present invention relates to a photo-record player, and more particularly, to an apparatus for controlling eccentricity in a photo-record player and a control method thereof which are applicable to normal servo or seek by measuring an eccentricity ratio and an eccentricity phase of a photo-record media.
2. Background of the Related Art
Generally, a photo-record medium, i.e. a photo-disc record player recording and regenerating a photo-disc, plays data recorded in a photo-disc using the photo-disc as a record medium such as CD (compact disc), DVD (digital versatile disc), and the like pr records data in the disc.
In order to find a demanded destination on the photo-disc, a laser beam generated from a pickup is moved to a target track precisely so as to be tracked on the target track, which is called xe2x80x98seekxe2x80x99or xe2x80x98searchxe2x80x99.
Such a seek operation is carried out in a manner that an entire photo-pickup is moved near a demanded track by driving a sled motor when a count of tracks to be jumped is hundreds to thousand in accordance with the calculation of the count of the tracks to a target track and that the demanded track is found using a tracking actuator if a count of remaining tracks is below several hundreds. In this case, xe2x80x98jumping tracks by moving the sled motorxe2x80x99is called xe2x80x98rough seekxe2x80x99, while xe2x80x98jumping tracks by moving the actuatorxe2x80x99is called xe2x80x98fine seekxe2x80x99.
FIG. 1 illustrates a block diagram of a general photo-disc recorder/player.
Referring to FIG. 1, a photo-pickup 102 makes a light beam, which is focused on a substance lens by a control of a servo control unit 104, placed on a signal track of a photo-disc 101, focuses an incident light reflected on a signal record surface, on the substance lens again, and then makes the light incident to a photo-detector to detect a focus error signal and a tracking error signal.
The photo-detector includes a plurality of photo-detecting devices and outputs electric signals proportional to the light intensity attained by the respective photo-detecting devices to an RF/servo error generating unit 103.
The RF/servo error generating unit 103 detects an RF signal for data regeneration, a focus error signal FE for servo control, and a tracking error signal TE from the electric signals detected from the respective photo-detecting devices.
The detected RF signal is outputted to a data decoder (not shown in the drawing) for play, and servo error signals such as FE and TE are outputted to a servo control unit 104.
The servo control unit 104 carries out a signal processing on the focus error signal FE so as to output a driving signal for a focusing control to a focus servo driving unit 105, and carries out a signal processing on the tracking error signal TE so as to output a driving signal for a tracking control to a tracking servo driving unit 106.
In this case, the focus servo driving unit 105 drives a focus actuator in the photo-pickup 102 in accordance with the focus driving signal to move the photo-pickup 102 up and down so that the photo-disc 101 rotates to follow the up and down movement correspondingly.
The tracking servo driving unit 106 drives a tracking actuator in the photo-pickup 102 in accordance with the focus driving signal so as to amend a location of a beam by moving the substance lens of the photo-pickup in a radial direction, thereby tracking a predetermined track. In this case, on a normal record/play operation or fine seek, the substance lens of the photo-pickup 102 is moved in the radial direction by driving the tracking actuator.
Meanwhile, in xe2x80x98rough seekxe2x80x99that the photo-pickup is moved entirely, the sled servo driving unit 107 receives a sled control signal from the servo control from the servo control unit 104 so as to transport a body of the photo-pickup 102 directly in a demanded direction by driving the sled motor 108.
Moreover, the servo control unit 104 detects revolution speed information of a disc from the RF signal so as to output the information to a spindle servo 109. The spindle servo 109 then carries out a phase locked loop (PLL) control on a spindle motor 110 in accordance with the revolution speed information so as to revolve the disc 101. Namely, the spindle motor 110 gives a spindle (not shown in the drawing) a turning force for the revolution of the disc 101, and then the spindle transfers the turning force given by the spindle motor 110 to the disc 101, thereby enabling to revolve the disc 101 at a demanded speed.
In this case, the photo-disc 101 may be distorted during projecting and hardening steps of a resin in a manufacturing process. And, the distortion may causes eccentricity despite piercing a hole in a center of the disc. Moreover, tracks of the disc, even if recorded precisely with a spiral figure with pitches of a determined standard, may bring about eccentricity due to deviation of the center hole. As the disc revolves with the eccentricity, a central axis of a motor barely coincides with a center of each of the tracks. Namely, the original disc center fails to coincide with the track center.
Particularly, there are disc eccentricity occurring in manufacturing a disc, eccentricity occurring in mounting the disc, and eccentricity due to xe2x80x98run-outxe2x80x99of a revolving axis. Besides, the quantity by xe2x80x98run-outxe2x80x99of a photo-axis is relatively much smaller than a quantity of the eccentricity caused by each of the foregoing two factors.
Thus, it is difficult to precisely read a signal of a demanded track only. Hence, the eccentricity should be controlled. Specifically, if it fails to control the eccentricity, a seek location becomes inaccurate. Inevitably, a destined location is found by carrying out a number of track jumps to xe2x80x98fine seek. Therefore, a seek time is taken longer.
In a method of controlling eccentricity according to a related art, a quantity of eccentricity is measured when a track control loop is configured and then a control degree (i.e. servo gain) of a track loop is adjusted in accordance with the measured quantity of the eccentricity.
FIG. 2 including (a), (b), and (c) illustrates graphs of waveforms of a TE signal, a track zero crossing (TZC) signal at this time, and an FG signal which are measured on pre-running status.
The TZC signal in FIG. 2(b) is a signal turned on/off at a track crossing time point, and is attained by slicing the TE signal in FIG. 2(a) into internal reference levels. And, the FG signal in FIG. 2(c) is a frequency generating (FG) signal, in which the frequency is generated from spindle revolution. In this case, a count of FG signals generated from one revolution of the spindle may vary in accordance with designer""s choice. In the drawing, it is assumed that a count of the FG signals during one spindle revolution, i.e. one revolution of a photo-disc, as shown in FIG. 2(c), is six.
In this case, when the photo-disc is inserted, a quantity of eccentricity is measured by the following Formula 1 at a pre-running state that a tracking servo and a focus servo are turned off and on, respectively.
[Formula 1]
a quantity of eccentricity=(TZC count per revolution of photo-disc)xc3x97Tpxc3x97xc2xd, 
where Tp is a track pitch. And, Tp of DVD is 0.74 mm.
FIG. 3 illustrates a diagram for explaining a track jump in a general photo-disc structure such as DVD and finding a quantity of eccentricity at this time.
Namely, an absolute measurement of eccentricity is attained by counting TZC (track zero crossing) signals generated by one spindle revolution during pre-running. The one spindle revolution is known by counting the number of FG signals as shown in FIG. 2(c).
Such a measured quantity of eccentricity is always constant while the disc is loaded.
The above-mentioned method enables a follow-up for a general track control but fails to be applicable to a xe2x80x98seekxe2x80x99with no track control. Hence, an error of a seek location becomes excessive when eccentricity is large, thereby affecting greatly an access time delay. And, eccentricity fails to be followed up unless a servo tracking gain increases. Then, the RF signal is not properly detected, thereby degrading record/play signals.
Moreover, the quantity of eccentricity attained by the above method is absolute, while a control quantity of each controller is relative. Hence, gain and filter coefficients in the corresponding controller should be changed, whereby a servo becomes unstable and hardware becomes complicated.
Accordingly, the present invention is directed to an apparatus for controlling eccentricity in a photo-record player and control method thereof that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an apparatus for controlling eccentricity in a photo-record player and control method thereof, which detects a quantity and a phase of eccentricity from periodicity of TE generated from one revolution of a disc, determines an eccentricity control quantity using the quantity and phase of eccentricity, and applies the eccentricity control quantity to a normal servo.
Another object of the present invention is to provide an apparatus for controlling eccentricity in a photo-record player and a control method thereof which detects a quantity and a phase of eccentricity from periodicity of TE generated from one revolution of a disc, determines to store an eccentricity control quantity using the quantity and phase of eccentricity, and applies the eccentricity control quantity to a seek.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of controlling eccentricity in a photo-record player measuring to control the eccentricity when a photo-record medium is inserted according to the present invention includes a step (a) of detecting an eccentricity quantity from a size of a tracking error signal generating per one revolution of the photo-record medium after on-track, a step (b) of detecting an eccentricity phase from a periodicity of the tracking error signal generating per one revolution of the photo-record medium, and a step (c) of generating an eccentricity compensating value from the eccentricity quantity of the step (a) and the eccentricity phase of the step (b) so as to compensate a tracking driving voltage driving a tracking actuator.
Preferably, the eccentricity quantity is detected from a peak-to-peak voltage of the tracking error signal in the step (a).
Preferably, the eccentricity phase is detected from a peak-to-peak voltage of the tracking error signal in the step (a).
Preferably, the periodicity of the tracking error signal in the step (b) is verified by a period signal generating regularly with a predetermined time interval when the photo-record medium revolves after the on-track.
Preferably, the period signal is a frequency generating (FG) signal.
Preferably, the eccentricity phase in the step (b) is detected from a phase difference between the FG signal generating per one revolution of the photo-record medium and the tracking error signal occurring simultaneously.
Preferably, the eccentricity phase in the step (b) is detected from a periodicity of the tracking driving voltage generating per one revolution of the photo-record medium.
Preferably, the eccentricity compensating value in the step (c) is generated using the following formula: eccentricity compensating value=A sin{2xcfx80(mt/(nT)+xcfx86), where A is the eccentricity quantity, xcfx86 is the eccentricity phase, n is a count of FG signals generating per one revolution of the photo-record medium, and m is a location of the FG signal when the size of the tracking error signal is maximum.
Preferably, the tracking driving voltage in the step (c) is generated from a value attained by adding the tracking error signal to the eccentricity compensating value on normal servo.
Preferably, the compensating value in the step (c) is stored therein and then the tracking driving value is generated only from the compensating value having been stored on seek.
In another aspect of the present invention, an apparatus for controlling eccentricity in a photo-record player, the apparatus measuring to control the eccentricity when a photo-record medium is inserted, the apparatus includes an eccentricity detecting unit detecting an eccentricity quantity from a size of a tracking error signal inputted after on-track and detecting an eccentricity phase from a phase difference between the tracking error signal and a period signal generating per one revolution of the photo-record medium with a predetermined interval, a compensating signal generating unit receiving the eccentricity quantity and phase so as to generate to store an eccentricity compensating value, and a servo unit carrying out a tracking servo by compensating a tracking driving voltage with the eccentricity compensating value outputted from the compensating signal generating unit.
Preferably, the eccentricity detecting unit detects the eccentricity quantity from the tracking error signal or a peak-to-peak voltage of the tracking driving voltage.
Preferably, the period signal of the eccentricity detecting unit is a frequency generating (FG) signal.
Preferably, the compensating signal generating unit generates the eccentricity compensating value using the following formula: eccentricity compensating value=A sin{2n(mt/(nT)+xcfx86), where A is the eccentricity quantity, xcfx86 is the eccentricity phase, n is a count of FG signals generating per one revolution of the photo-record medium, and m is a location of the FG signal when the size of the tracking error signal is maximum.
Preferably, wherein the servo unit carries out the tracking servo by adding the eccentricity compensating value outputted from the compensating signal generating unit to the inputted tracking error signal on normal servo and by generating the tracking driving voltage with a result of the adding.
Preferably, the servo unit carries out the tracking servo on seek by generating the tracking driving voltage with the compensating value stored in the compensating signal generating unit only.
Preferably, the apparatus further includes a switching unit installed at a front stage of the eccentricity detecting unit so as to interrupt an output of the tracking error signal by being turned off.
In a further aspect of the present invention, a method of controlling eccentricity in a photo-record player measuring to control the eccentricity when a photo-record medium is inserted includes a step (a) of detecting an eccentricity quantity from a peak-to-peak voltage of a tracking error signal induced per one revolution of the photo-record medium after on-track, a step (b) of detecting an eccentricity phase from a periodicity of the tracking error signal generating per one revolution of the photo-record medium, a step (c) of receiving the eccentricity quantity and the eccentricity phase so as to generate to store an eccentricity compensating value, and a step (d) of generating a tracking driving voltage with the stored compensating value only on seek so as to drive a tracking actuator.
Preferably, the periodicity of the tracking error signal in the step (b) is verified by a FG (frequency generating) signal generating per one revolution of the photo-record medium after the on-track.
Preferably, The apparatus of claim 18, wherein the eccentricity compensating value in the step (c) is generated using the following formula: eccentricity compensating value=A sin{2xcfx80(mt/(nT)+xcfx86), where A is the eccentricity quantity, xcfx86 is the eccentricity phase, n is a count of the FG signals generating per one revolution of the photo-record medium, and m is a location of the FG signal when the size of the tracking error signal is maximum.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.